Synthesis of Silicon and Germanium-Containing Heterosumanenes via Rhodium-Catalyzed Cyclodehydrogenation of Silicon/Germanium–Hydrogen and Carbon–Hydrogen Bonds

A three-step synthesis of C3-symmetric trisilasumanene and trigermasumanene, heteroanalogues of the π-bowl sumanene, was achieved using a threefold rhodium-catalyzed cyclodehydrogenation of Si/Ge–H and C–H bonds as the key step. Trigermasumanene was proven to adopt a planar geometry by single crystal X-ray diffraction for the first time. The optical properties were also investigated by UV–vis and fluorescence spectroscopy.